CHROMOSOME 11Q23 ABNORMALITIES IN LEUKEMIA

Breakpoints on chromosome 11 at band q23 have been observed in patient s with primary or secondary leukaemia. Recent data have shown that the se breakpoints are clustered in a similar to 15kb region of a gene nam ed HRX. This gene product has homology to the Drosophila trithorax gen e product, which suggests it may play a role in regulating transcripti on control. Disruption of HRX as a result of chromosomal translocation is thought to contribute to the leukaemogenic process; this may occur in utero giving rise to infant acute leukaemia or may be induced by e pipodophyllotoxic drugs resulting in secondary leukaemia. Translocatio ns of 11q23 can involve a number of different partner chromosomes. The reciprocal genes on chromosomes 4q21, 9p22 and 19p13 have been recent ly cloned and are predicted to encode proline and serine rich proteins . Of particular interest is the high degree of homology observed betwe en the genes on 9p22 and 19p13, which suggests that they too may have an important role to play in the generation of the leukaemic phenotype .